The present invention is directed to an apparatus for preventing contamination of a bicycle control cable and, more specifically, to a protective cap system for preventing deterioration of the cable as a result of the penetration of foreign matter.
Bicycle front and rear brakes and derailleurs are operated by control cables connected to shift lever units or brake levers located on the handle bars. The control cables comprise an inner cable that is slidingly disposed within an outer casing. The inner cable is made by twisting several steel wires together. The outer casing is ordinarily constructed of a synthetic resin cable liner, a band steel strip that is spirally wound around the cable liner, and a synthetic resin jacket that is used to cover the outer circumference of the band steel strip.
The outer casing usually terminates at a position between the shifting lever unit or brake lever and the rear or front derailleur, thus leaving the inner cable exposed.
Unfortunately, foreign objects such as mud, dust, etc., penetrate from the exposed end of the cable, thus increasing the slide resistance between the inner cable and cable liner. As a result, the brakes or shift mechanism, etc., becomes more difficult to operate. Furthermore, foreign objects such as clay and sand in mud act as grinding materials, causing the cable liner and inner cable to wear more quickly. Contamination of the gap between the inner cable and the outer casing thus should be avoided wherever possible.
FIG. 1 shows a known protective cap 10 having a rigid first section 12 which fits over the free end of an outer casing 14 of a control cable 18. Cap 10 also has a rigid second section 22 with an inner diameter slightly larger than an outer diameter of an inner cable 26. Unfortunately, cap 10 still has a gap 30 between the inner surface of second section 22 and the outer surface of inner cable 26, and gap 30 widens when the inner cable 26 flexes in the radial direction shown in the figure. The widened gap increases the chance that contaminants will enter the control cable.
FIG. 2 shows another known protective cap 40 which fits over the free end of outer casing 14 of control cable 18. Protective cap 40 includes a generally toroidally shaped resilient seal 48 extending radially inwardly from a rigid peripheral wall 44. While this structure is ordinarily satisfactory when the inner cable extends straight from outer casing 14, a gap 50 forms when inner cable 26 flexes in the radial direction, since the position of seal 48 is fixed by the rigid wall 44. Gap 50 allows contaminants to enter the control cable.